You may have duplicate families in the system and both records may have contributions. No problem! Here's how you can combine them together and remove the duplicate...
You'll want to decide which of the duplicate records you want to keep and which you'll want to delete. For example, if you have a William Smith and a Bill Smith, you may choose to keep William Smith and delete Bill.
From your CMS Contribution System, click Find People | click the Go To Person button at the top of the Find screen and choose Summary | now find the record that you want to keep, i.e. William Smith.
This should take you to William's Summary screen. From the pull down menu at the top of the screen, click Record | Combine.
Find the record you wanted to delete, i.e. Bill Smith, highlight that name and click OK.
The system will ask if you're sure, answer Yes.
Now all of the contributions, history and pledge information are now moved to the one record!
Next, click Find and find the record you want to Delete. Click the Delete (garbage can) icon at the top of the screen to permanently delete this duplicate record from the system.